The transient electric birefringence behavior of bacteriophage T2 and the T2 ghost or protein coat was studied. The field free relaxation measurements show both the intact virus and its ghost to have two rotary diffusion coefficients. These coefficients have values of 555 f 54 and 111 f 22 sec.-1 for the intact virus and 688 f 89 and 161 f 29 sec-1 for the ghost. The equivalent ellipsoids for the fast and slow relaxation coefficients were obtained by use of Perrin's equation and were related to the bacteriophage structure in terms of a possible extension of the tail fibers or an enlargement of the head structure. The saturation of the specific birefringence of the phage and the ghost when compared with the specific birefringence of the free nucleic acid gave an average optical orientation of 10 to 18% of the nucleic acid parallel to the main axis of the phage. The analysis of the birefringence versus applied field strength in the Kerr region gave the following values for the anisotropy of the polarizability, 0 1 . ~3 -0 1 ~, ~~, and intrinsic dipole, p, of both phage and ghost: for T2 phage a e , 3 3ac,1l = 5.0 X 10-14 cm.3 and p = 64,400 Debyes; for T 2 ghost ole,33ae,ll = 7.9 X lo-'* c m 3 and p = 57,200 Debyes. The high intrinsic dipole for phage and ghost is interpreted as to be associated with the mechanisms of the virus for attachment to the host cell wall.